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Kling 4.0 Flash cost (2026): $0.094/sec at 720p, usable 30s price and the input-video billing trap
Kling 4.0 Flash is live on Kling’s own developer API at $0.094 per second (720p, no input video). Here is the verified rate, the usable-30s cost with retries, how it compares with full Kling 4.0 and the Runway promo, and why the with-input $0.063 unit price is not a discount.
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Quick answer
Kling 4.0 Flash is $0.094/sec at 720p with no input video on Kling’s own API — $2.82 per 30s try, $8.46 per usable 30s with 2 retries (#91 of 237 ranked rates; API #79). Full Kling 4.0 on the same API is now live at $0.157/sec 720p ($14.13 usable, #154) and $0.235/sec 1080p ($21.15 usable). The Runway API Kling 4.0 720p promo is ~$11.30 usable through Nov 30, 2026 UTC. Flash is 720p only, 3–20s per request, and lists no native audio. Checked Nov 7, 2026 (~9am Central) on Kling’s official video pricing Markdown and Flash text-to-video docs.
New Nov 7, 2026 (9am): Kling 4.0 Flash + live Kling 4.0 no-input rates added to calculator data under tool klingapi. Counts now 17 tools / 246 models / 237 ranked / 193 API. Dedicated page: this URL. See also Kling 4.0 cost (Runway promo still listed) and Kling API pricing.
Basis: usable = 3 attempts (1 + 2 retries). Ranked rates use the no input video unit prices only. With-input billing is explained below and is not ranked as a plain $/sec. Cost only — no quality ranking.
Verified Kling API rates (no input video)
| Rank of 237 | Model | $/sec | 5s try | 10s try | 15s try | 20s try | 30s try | Usable 30s (2 retries) | API # |
|---|---|---|---|---|---|---|---|---|---|
| 91 | Kling 4.0 Flash · 720p, no input video | $0.094 | $0.47 | $0.94 | $1.41 | $1.88 | $2.82 | $8.46 | API #79 |
| 154 | Kling 4.0 · 720p, no input video | $0.157 | $0.79 | $1.57 | $2.36 | $3.14 | $4.71 | $14.13 | API #140 |
| 181 | Kling 4.0 · 1080p, no input video | $0.235 | $1.18 | $2.35 | $3.53 | $4.70 | $7.05 | $21.15 | API #157 |
Maths: $/sec × seconds. Flash example: $0.094 × 30 = $2.82 per try; × 3 = $8.46 usable. Flash maxes at 20s per request, so a 30s video is at least two generations.
Cost per length (Flash vs Kling 4.0 vs Runway promo)
| Length | Flash 720p try | Flash usable (3×) | Kling 4.0 720p API try | Runway Kling 4.0 720p promo try |
|---|---|---|---|---|
| 5s | $0.47 | $1.41 | $0.79 | $0.63 |
| 10s | $0.94 | $2.82 | $1.57 | $1.26 |
| 15s | $1.41 | $4.23 | $2.36 | $1.88 |
| 20s | $1.88 | $5.64 | $3.14 | $2.51 |
| 30s | $2.82 | $8.46 | $4.71 | $3.77 |
Input-video billing trap (do not treat $0.063 as the ranked rate)
Kling 4.0 and Kling 4.0 Flash bill differently when you attach a reference / feature / base video or a video character element:
- When input duration ≤ output duration: Unit price × output × 2
- When input duration > output duration: Unit price × (input + output)
| Scenario | Listed unit $/sec | Billed duration | Effective cost |
|---|---|---|---|
| Flash · no input | $0.094/s unit price | output duration | $0.094 × output |
| Flash · with input, input ≤ output | $0.063/s unit price | output × 2 | $0.063 × output × 2 = $0.126 × output (dearer than no-input) |
| Flash · with input, input > output | $0.063/s unit price | input + output | $0.063 × (input + output) |
| Kling 4.0 720p · no input | $0.157/s unit price | output duration | $0.157 × output |
| Kling 4.0 720p · with input, input ≤ output | $0.094/s unit price | output × 2 | $0.094 × output × 2 = $0.188 × output |
Worked example: 10s Flash output with a 5s input video bills 10 × 2 = 20s at $0.063 = $1.26 — more than the same 10s with no input at $0.094 = $0.94. The 0.4-unit “discount” is not cheaper for typical equal-or-shorter inputs.
Limits
- 720p only for Flash (
settings.resolutionenum720p). - Duration 3–20 seconds (integer enum); default 10s if omitted and not identified in the prompt.
- No native-audio row on the Flash pricing table.
- Endpoint:
POST /text-to-video/kling-4.0-flash. - Aspect ratios: 21:9, 16:9, 9:16, 1:1.
Vs peers (usable 30s)
| Option | $/sec | Usable 30s |
|---|---|---|
| Grok Imagine 1.5 Lite 480p (xAI API) | $0.02 | $1.80 |
| PixVerse V6 360p silent | $0.0222 | $2.00 |
| MiniMax H3-Lite 480P | $0.025 | $2.25 |
| PixVerse V6 720p with audio | $0.0533 | $4.80 |
| Kling 3.0 720p silent (Kling app) | $0.06 | $5.40 |
| Kling 3.0 720p silent (Kling API) | $0.084 | $7.56 |
| Kling 4.0 Flash 720p no-input (this page) | $0.094 | $8.46 |
| Kling 3.0 Omni / O3 peers | $0.112 | $10.08 |
| Kling 4.0 720p Runway API promo | $0.1256 | $11.30 |
| Kling 3.0 720p with audio (Kling API) | $0.126 | $11.34 |
| Kling 4.0 720p no-input (Kling API, this page) | $0.157 | $14.13 |
More: cheapest AI video API, AI video API pricing, Kling 3.0 cost, Runway API partner models, Kling O3 cost.
Traps
- With-input unit price is not a discount — see the ×2 / input+output rules above.
- 720p only on Flash; need 1080p? Use full Kling 4.0 ($0.235/sec no-input) or another model.
- 20s cap per Flash request — 30s means stitching (and retrying) multiple gens.
- Prepaid units expire; unused package balance is cleared when the package expires.
- Runway promo ≠ Kling API list — Runway’s 20% Kling 4.0 promo (through Nov 30, 2026 UTC) is a separate storefront; Flash is Kling-API-native.
Which to pick (on cost)
- Cheapest Kling 4.x on Kling’s API: Flash 720p no-input ($8.46 usable) — if 720p/20s/no listed audio is enough.
- Need 1080p on Kling’s API: full Kling 4.0 1080p no-input ($21.15 usable).
- Already on Runway credits: Kling 4.0 720p promo (~$11.30 usable) through Nov 30 UTC; list from Dec 1 matches Kling API $0.157 ($14.13 usable).
- Still cheaper Kling overall: Kling 3.0 in the app ($5.40 silent / $8.10 with audio usable at 720p) or Kling 3.0 API silent ($7.56 usable).
Related: calculator · Kling 4.0 cost · Kling API pricing · Kling API traps · Kling app pricing · Kling 3.0 · Runway API partners · AI video API pricing · Cheapest AI video API · Compare · FAQ.
Sources (checked Nov 7, 2026, about 9am Central)
- Kling API video pricing (Markdown) — Kling 4.0 Flash 0.6 Units ($0.094)/s 720p no-input; with-input 0.4 Units ($0.063)/s + duration rules; Kling 4.0 1.0 / 1.5 Units ($0.157 / $0.235)/s no-input at 720p / 1080p.
- Kling API video pricing (HTML) — same table (JS-rendered; Markdown used for verification).
- Kling 4.0 Flash text-to-video API — duration enum 3–20s; resolution 720p only; default 10s; POST /text-to-video/kling-4.0-flash.
- Runway API pricing — Kling 4.0 promo credits (comparison only; through Nov 30, 2026 UTC).
FAQ
How much does Kling 4.0 Flash cost per second?
On Kling's own API (checked Nov 7, 2026 on kling.ai/document-api/pricing/base/video.md): Kling 4.0 Flash with no input video is 0.6 Units ($0.094) per second at 720p only. There is no 1080p/4K row and no native-audio row for Flash. A 30-second try is $2.82 and a usable 30s clip with 2 retries is $8.46 (#91 of 237; API #79).
What does a usable 30-second Kling 4.0 Flash video cost?
$8.46 with 2 retries (3 attempts) at the no-input 720p rate. One 30s try is $2.82. Flash clips are 3–20 seconds per request (settings.duration enum on the text-to-video docs), so a 30s video needs at least two generations stitched together.
Is the Flash with-input price ($0.063/sec) cheaper?
No — that is the unit price trap. When input duration ≤ output, Kling bills unit price × output × 2 (so 0.4 Units × 2 = effective $0.126/sec, dearer than the $0.094 no-input rate). When input > output, it bills unit price × (input + output). ClipCost ranks only the no-input-video rates.
How does Kling 4.0 Flash compare with full Kling 4.0 and the Runway promo?
Flash at $0.094/sec ($8.46 usable) undercuts full Kling 4.0 on Kling's API at $0.157/sec ($14.13 usable, #154) and undercuts the Runway API Kling 4.0 720p promo at $0.1256/sec (~$11.30 usable) — but Flash is 720p-only, 3–20s, and lists no native audio. Full Kling 4.0 on Kling's API is now live at $0.157 / $0.235 (720p / 1080p, no input).
Is Kling 4.0 still Coming Soon on Kling's API?
No. As of Nov 7, 2026 the official video pricing page lists Kling 4.0 and Kling 4.0 Flash as live billed models (not Coming Soon / TBA). Runway's separate 20% Kling 4.0 promo (12.56 / 18.8 credits/sec) still runs through Nov 30, 2026 UTC.
What are the Flash limits?
Resolution enum is 720p only. Duration enum is integers 3–20 seconds (default 10s when omitted and not stated in the prompt). Path: POST /text-to-video/kling-4.0-flash. Aspect ratios: 21:9, 16:9, 9:16, 1:1. Checked on Kling's Flash text-to-video docs the same morning as the price check.